On March 29, 2022, the Long March 6A launch vehicle developed by the Shanghai Academy of Spaceflight Technology successfully made its maiden flight at the Taiyuan Satellite Launch Center. The Long March 6A launch vehicle was China’s first solid bundled rocket. It uses non-toxic and non-polluting propellants, and has a 700 km sun-synchronous orbit carrying capacity of no less than 4.5 t, which is more than 50% higher than that of a LM-4C launch vehicle. During the development of the LM-6A launch vehicle, the matching relationship between systems and the overall performance of the entire rocket improved significantly through continuous overall optimization work. This paper introduces the typical overall optimization work during the development of the LM-6A launch vehicle.

Optimal design of the tank has a significant effect on reducing the weight of a launch vehicle’s structure. In this paper, the key characteristics of a stiffened shell are dentified from the design requirements, focusing on the influence of the internal pressure on the axial compression load-bearing capacity. The computing method of the ultimate load of the stiffened shell, the parametric modeling method and the surrogate modeling technique for optimal design are reviewed. An optimization process applicable to the stiffened shell was developed and applied in the optimization work for the tanks of solid-liquid bundled launch vehicle, so a better weight reduction effect could be achieved.

Liquid bipropellant attitude control rocket engines are widely used in satellites, manned spaceships, deep space probes and other spacecraft. The performance of an attitude control engine is directly related to the lifetime, control precision and safety of a spacecraft. The study of flow characteristics of an engine transient process is important 
to improve its performance. In this paper, the transient flow test of a transparent test piece was carried out during the starting process of the attitude control engine. Then the transient process of the test piece was simulated and compared with the test results to verify the rationality of the simulation model. Transient flow simulation was carried out for the starting process of the real engine injector. The results show that the filling of the outer ring of the oxidant circuit is slower than that of the central collecting cavity, and the filling of the second layer of the outer ring is slower than that of the first layer. The filling process in the fuel path starts from the cooling hole near the inlet side and the fuel flows out in the circumferential direction. Installation direction has little influence on engine starting flow process in the ground state. 
The filling time of the engine in its vacuum state is longer than that in the ground state, the filling time of oxidizer is 31% longer than that in ground state, and the filling time of fuel is 57% longer than that in ground state.

Human Mars exploration has significant values in terms of exploring extraterrestrial life, interplanetary immigration, promoting science and technology development, and the progress of human society. This paper summarizes the research progress on human Mars exploration and the corresponding proposed space transportation systems in the world, and analyzes the development trends. A preliminary scheme including the human Mars exploration mission architecture and corresponding space transportation system is then proposed, and the related key technologies are identified. The results can be a reference for future further research.

In the recovery process of the reusable rocket with vertical take-off and landing, it has to go through the active control process, such as power drop, hover and vertical landing. The key technology lies in the development of high-precision vertical recovery control algorithm. Therefore, a vertical take-off and landing reusable launch vehicle prototype is developed to verify the rationality of the flight control algorithm of rocket vertical recovery.
The vertical take-off and landing reusable launch vehicle prototype is 0.45 m long, 0.45 m wide, 0.6 m high, and has 23 kg take-off weight with a maximum thrust of 400 N jet engine as the power plant, through four gas rudders to achieve the aircraft pitch and yaw and roll-on control. The prototype focuses on the verification of the guidance and control algorithm of the vertical recovery algorithm. Therefore, it is equipped with the vector control capability, avionics and measurement system similar to that of the vertical recovery rocket. The prototype can be used for verification of the flight control algorithm.

China’s Chang’e 3 (CE-3) and Chang’e 4 (CE-3) missions made historic progress by sending rovers equipped with scientific instruments to the new sites on the nearside and farside of the moon, respectively. The same lunar penetrating radar (LPR) that uses pulses of electromagnetic energy to reveal the underground structure and properties of the lunar soil “regolith” covering most of the lunar surface was carried by the rovers. It provided for the first time the opportunity for in situ LPR measurements of the subsurface substrate in two geologically different places on the moon. 
At present, the Yutu rover of CE-3 mission traveled along a path of total length of about 114 m while the Yutu 2 rover of CE-4 has traversed over 1000 m and keeps going. This paper summarizes the fruitful results so far obtained by LPRs, including the physical properties and layered structure of the lunar regolith and shallow crust beneath the two landing sites. The regolith layer thickness at the CE-3 site is thinner than that at the CE-4 site due to its relatively young age. The penetration depth below CE-4 site is about 2.85 times (in terms of the forward and return path delay) deeper than CE-3 as indicated by their different loss tangent values (0.0039 ± 0.0002 vs. 0.013), which is probably due to the differences in abundance of ilmenite and rocks in the regolith. Other physical parameters including dielectric permittivity vs. depth profile, bulk density and electrical conductivity have been estimated using various methods. Thanks to the low signal loss, CE-4 LPR is able to present clear cross section views of two buried craters and the paleo-surface (ancient surface) of the landing site. The multiple stratums observed by the low frequency channel of LPRs indicate several episodes of lava eruptions occurred in the late stage of the formation of the nearside Imbrium Basin and the farside Von Kármán crater despite the asymmetric volcanisms distributed on two sides. 
The discoveries revealed by LPRs advance our knowledges on the formation process and roperties of lunar regolith, thickness of ejecta deposits caused by lunar impact events, the evolution of the nearside and farside volcanisms, etc. They also demonstrate the feasibility of applying ground penetrating radar for non-terrestrial explorations such as China’s first Martian mission, Tianwen 1 mission. 

In order to realize a high-precision and continuous working function of a star sensor, we propose a new 
optical system design. Considering the difficulty of the manufacturing process, the entire optical system uses a complicated Petzval structure. In this paper, the key design elements of the optical system applied for star sensors are presented and the most important performance parameters are given. The ground test results show that the system can maintain excellent detection performance on a near-surface atmospheric platform. This study provides an optical system design scheme for a high-precision and continuous operating star sensor, as well as the theoretical basis for future in-atmosphere and continuous star detection technology.

The indigenous developed global BeiDou Navigation System (BDS-3) was formally commissioned, marking the completion of the three-step BDS development strategy, and a new era for BDS to better serve people from all walks of life. In this paper, the recent progress and main characteristics of BDS technology fusion and industry integration are analyzed. The discussion on the latest development on “BDS+” application starts from “BDS+Technology”and “BDS+Industry”, through to the future prospective BDS applications.

The completion of the BeiDou global navigation satellite system has made China becoming the third country owning a global navigation satellite system independently. It has embarked on a development path with Chinese characteristics, enriched the development route of the world navigation satellite system, and enhanced China’s core competitiveness.
The article describes the development and construction of Beidou Navigation Satellite System (BDS) and summaries the main achievements of BDS-1, BDS-2 and BDS-3 systems from the three aspects of independent innovation,system research and technological breakthrough. The article also analyzes the technical innovation characteristics of the BDS satellites comprehensively, providing a reference for subsequent research and planning of the next generation of the BDS satellites that are more ubiquitous, more integrated, and more intelligent.

The LM-3A series launch vehicle was used for all launch missions for the BeiDou Navigation Satellite System (BDS) project, including BDS-1, BDS-2, and BDS-3. So it is known as Space Express for BDS. During the 26 years’ development period for the BDS project, a series of key technological breakthroughs with the LM-3A series of launch vehicles were made, improving the launch capability of different payloads into GTO, IGTO and MTO, from sending one satellites into transfer orbit to sending two satellites into transfer orbit, to sending two satellites into target orbit directly. A total of 59 satellites in 44 launches were launched using the LM-3A series launch vehicle for the BDS project, achieving 100% success.

China’s BeiDou Navigation Satellite System (BDS) construction has been completed and the system has been formally commissioned. Most of the Electric Power Systems (EPSs) for MEO satellites were developed by the Shanghai Institute of Space Power-sources. The 42 V medium-voltage fully-regulated high-power EPS has been adopted for the first time in medium Earth orbit, with an output power reaching about 3 kW. Compared with the 42 V medium-voltage semi-regulated bus power system used in the Regional Navigation BDS-2 satellite, the EPS of the BDS-3 MEO satellites has increased power by about 80%, adopting many newly developed products such as high-efficient triple junction GaAs solar cells, high-energy-density lithium ion batteries and a high-efficient autonomous power control unit (PCU). Based on the studies on the medium-voltage fully-regulated and high-power EPS technical principles, and the adaptability and reliability of various working modes, the test verifications for the EPS were conducted both on the ground and in orbit. Compared with other global navigation satellite systems such as GPS, Galileo and GLONASS, the EPS of the BDS-3 MEO satellite has a long design life time which is equivalent to that of the GPS and Galileo, but with a larger power supply capability and power ratio, distinguishing its advancement in the field of satellite power technology.

Satellite laser ranging (SLR) is an unambiguous measurement technique and generates high accuracy satellite orbit data. All satellites in the BeiDou navigation satellite system (BDS) carried laser retro-reflector arrays (LRAs), so they can be tracked by ground SLR stations in order to provide the accurate observation data. The Shanghai astronomical observatory (SHAO) designed the LRAs, and also developed the dedicated SLR systems using a 1 m-aperture telescope and a transportable cabin-based SLR system with a telescopes of 60 cm aperture. These enable BDS satellite ranging during daytime and nighttime with centimeter-level precision, allowing highly accurate estimations of satellite orbits. Moreover, some of the BDS satellites are also equipped with laser time transfer (LTT) payloads, which were developed by the SHAO and China Academy of Space Technology (CAST), providing a highly accurate time comparison between the satellites and ground clocks. This paper describes the dedicated SLR system and the design of the LRAs for BDS satellites, as well as global SLR measurements. The SLR tracking data is used for evaluating the orbit accuracy of BDS satellites and broadcast ephemeris, with an accuracy of less than 1 m. The LTT measurements to BDS satellites for a single shot have a precision of approximately 300 picoseconds, with a time stability of 20 picoseconds in 500 s.

 With the development of satellite navigation technology, the user demands for the integrity of Global Navigation Satellite System (GNSS) have increased more and more. A ground-based monitoring system can hardly report an alarm message to GNSS users during the valid alarming period due to the satellite-Earth propagation delay. It is beneficial to monitor abnormal events and report the corresponding alarms from orbit. Adopting this approach, which is an important feature for future GNSS integrity monitoring, the time needed to provide an alarm is shorter and the system integrity capability is strengthened. The BeiDou Navigation Satellite System (BDS) new generation satellites have the capabilities of satellite autonomous integrity monitoring (SAIM). This paper presents the technical scheme of SAIM, and proposes the integrity monitoring method of both navigation signals and the clocks onboard. The proposed method was verified through the onboard test on the BDS satellites. In addition, we analyzed the integrity telemetry data from the new generation of BDS satellite, including signal delay, power, carrier phase measurement, correlation peak, consistency of pseudo-code and carrier phase, clock phase and frequency step. The analysis results indicated that the quality of the data on orbit met the requirements, and SAIM could monitor effectively any abnormal change of satellite clocks and navigation signal, generate rapidly an alarm message, and transmit it to the user. The alarm time was less than 6 s through the message, and 2 s through non-standard code (NSC). Finally, we present future opportunities for improving the SAIM technology of BDS.

The transportation industry is one of the largest users of the BeiDou Navigation Satellite System (BDS), characterized by multiple locations, long lines, wide range, and extensive mobility. The application of BDS in the transportation industry improves the development level of intelligent, safe, green and shared transportation. Based on the introduction of the application requirements and characteristics of BDS in the transportation industry, this paper systematically introduces the overall status of BDS in the transportation industry, covering highways, waterways, railways, civil aviation, and the postal service. Finally, the paper forecasts future applications of BDS in the field of transportation. It identifies within the transportation industry rich application scenarios for the cultivation of advanced technologies represented by BDS, enhancing transportation safety services and guaranteeing emergency communication, while improving the operation efficiency and management level of an integrated transportation system.

The United States was the first country in the world to develop a satellite navigation system, with rich experience in system management, R&D, operation, and satellite applications industry. It started the construction of the Global Positioning System (GPS) in 1973 and deployed the first satellite in 1978. It has successfully developed and deployed three series of GPS satellites with a total of seven models. The United States is now focusing on the research and development of cutting edge navigation technologies and constellation modernization, replacing old ones with new GPS III series of satellites and actively exploring and verifying the frontier navigation technologies represented through the Navigation Technology Satellite 3 (NTS-3). It is now upgrading the original ground-based operation and control system, actively developing and deploying the GPS Next Generation Operational Control System (GPS OCX), and upgrading the military user equipment supporting Military Code (M-Code). The U.S. attaches importance to multiple measures to improve the service performance of the GPS system and enhance the resilience of the system to provide positioning, navigation, and timing capabilities. In this context, the progress of the construction of GPS and the related technological innovations are separated out and analyzed, which will help the Global Navigation Satellite System (GNSS) solutions summarizing their experience and learning from each other’s development to better serve social progress and economic development.

It is an important scientific research activity in China to carry out near-space exploration and scientific experiments via aerospace carriers. Early near-space exploration projects mainly used aircraft, balloons, sounding rockets and Earth satellites to carry out space environment exploration. With the development of China’s space science and technology, microgravity science has become a frontier science that has developed rapidly in the past 20 years. With the continuous progress of national space science and technology, the demand for near-space exploration and scientific experiments is increasing year by year. In the next 2 to 3 years, many advanced science activities and the associated technologies need to conduct corresponding experimental research work. This paper mainly analyzes the significance
of scientific research and the ways to realize near-space exploration at home and abroad, and analyzes the directions and innovations that can be carried out in the future.

In the past two decades, the world’s unmanned aerial vehicle (UAV) industry has developed rapidly.Various kinds of UAVs have been used in military and civilian fields. Based on the characteristics of UAVs and the development of aerodynamics, this article analyzes the development of aerodynamic optimization design and dynamic numerical simulation technology, then lists engineering applications. Both erodynamic optimization design and dynamic numerical simulation have greatly shortened the UAV design period and reduced the research and design cost. These two methods gradually replace traditional methods such as wind tunnel test.

This article reviews Mars sampling and return technology, by retrieving and analyzing the patents of domestic and foreign sampling equipment and mechanism technology, Mars surface removal technology and ultra-high-speed light and small sample return technology. It conducts patent analysis from the macro-technical view down to the
micro-specific content view using statistical, quantitative and qualitative analysis methods. In the process of macro-analysis, it analyzes patent data from multiple perspectives such as time, region, technical composition, and applicants, and establishes the development trends for Mars sampling and return technology at home and abroad. In the process of micro-analysis, through the analysis and interpretation of key patents, we can learn the development priorities and development direction of foreign Mars sampling and return technology. This paper also proposes China’s Mars sampling and return technology development suggestions.

Liquid propellant rocket engines for a launch vehicle are an essential aerospace technology, representing the advanced level of hi-tech in a country. In recent years, China’s aerospace industry has made remarkable achievements, and liquid rocket engine technology has also been effectively developed. In this article, the development processes of China’s liquid rocket engines are discussed. Then, the performance features of China’s new generation liquid rocket engines as well as the flight tests of the new-generation launch vehicles are introduced. Finally, the development direction and the most recent progress of the next generation large-thrust liquid rocket engine is presented.